1. Field of the Invention
This invention relates to improvements in feeders for food extruders and particularly to a feeder for gravity feeding of flowable solids to an extruder while venting steam generated in the extrudate during the process of extrusion.
2. BACKGROUND ART
It is well known in the art to extrude various food products, particularly snack food products utilizing an auger or screw extruder which mixes and compresses materials and extrudes them through a die. In doing so the extrudate gets quite hot and there is considerable steam generated within the extruded materials. Examples of such well known commercially available food extruders are the Baker & Perkins MPF-50D sold by Baker Perkins of Saginaw, Mich. or twin screw extruders sold by Werner & Pfleiderer Corp. of Ramsey, N.J.
It is highly desirable to gravity feed divided solid material to the food extrudate within the extruder for various purposes. For example, in certain cases it is desirable to add divided solid materials, e.g., particulates such as grains or powder, to an extruder just prior to the extrudate exiting from the die. However, attempts to feed such materials through an open port or through known feeders result in the steam which is generated within the extruder condensing on the feeder walls and causing eventual build-up or blockage. Thus, there is need in the art for a feeder for a food extruder which could feed solid materials by gravity and eliminate the problem of blockage and build-up caused by venting steam.
While it is known in the art to feed flavor-determining components into a food extruder downstream of the main ingredient inlet (see feed device 8 in U.K. Patent Application G.B. No. 2149637 A), and it is known to vent steam from a downstream port in an extruder (see vent 20 in U.S. Pat. No. 4,642,241), as well as to remove volatiles such as steam in injection molding plastic extruders (see U.S. Pat. No. 4,636,084), no solution was known to the vexing problem of gravity feeding of solid materials into a food extruder of the type wherein steam generated within the extruder could cause build-up and blockage on the feeder walls.